Gyraf Audio G25 Vocalshape Recording Channel  From Gyraf

The Gyraf Audio G25 VocalShape is an elaborate all-in-one box for vocal recording. It is an all-tube unit, consisting of a tube preamplifier stage followed by a filter and tube equalizer section fed into a vari-mu compressor which in turn drives the output stage containing a single band of passive frequency-selective clipping. Every and all parameters optimized for – and only for – recording vocals. All active functions, all amplification stages processing your signal are based on old-fashioned thermionic valves.

PREAMPLIFIER

The topology of the G25 preamplifier is very much like the classic G9, in a version optimized for high-gain frame-grid tubes (6N23P/E88CC). The INPUT Switch selects between Line, Mic, and Mic+P48. The GAIN switch controls the amount of gain applied in 4 dB steps. Mic/Line inputs are floating transformer-balanced with a line load of ~10 kohms and a mic load of ~2 kohms. 48 phantom power can be switched on only to the mic input for powering condenser microphones.

The Instrument input jack on the front is a high-Z input that simply interrupts the connection to back panel Mic/Line connectors when a jack is inserted. The addition of this Instrument input was possible without in any way compromising the units usability for vocal recordings – it’s a left-over from early revisions that is kept in place because of popular demand.

Mic gain maxes at a bit more than +70 dB - plenty for your old beaten-up SM7. Line gain is generally some 27 dB under mic gain setting with Instrument input gain some 17 dB under mic. With all knobs set to 12 o’clock we see some +48 dB gain in mic mode, +21 dB in line mode.

EQUALIZER

The EQ section consists of a first-order HPF @50 Hz or 120 Hz, a High/Low shelving symmetric boost/cut Bax at 6 dB/oct combined with the Linear Tilt circuit from the G23 – adjustable between ±0 and 1 dB/Oct at its extremes.

VARI-MU COMPRESSOR

Copied from the G10, off course. Fixed 20ms Attack, variable release 50ms - 1.6sec, Threshold and Ratio functions are combined into one knob labeled unified Drive. Gain reduction read-out on meter.

DE-RESONANCE/CLIPPER

This stage, which is integrated into the unit’s output transformer, after the “Output Drive” control pot, is a frequency-selective clipping circuit. The topology is a simplified version of the G21 Infundibulum – with a handful of switchable frequency ranges selected for their usefulness for helping vocal trouble. The ALL position is simple full-spectrum schottky diode clipping.